Suppression of reflected signals from substrate as clutters for cell measurements using acoustic impedance microscopy

Recently, a method for estimating three-dimensional acoustic impedance profiles in cultured cells and human dermal organs was proposed by interpreting the reflected ultrasonic signal based on a 1-D transmission line model for acoustic impedance microscopy (AIM). However, AIM has a disadvantage that reflected signals from cells overlap with that from a reference substrate. Additionally, the amplitudes of the reflected signals from the specimens are significantly weaker than that from the substrate. In this paper, we proposed a new method for separation of those signals based on a concept of clutter filter, which had been developed for a color Doppler method in medical ultrasonic imaging. The proposed filter using singular value decomposition (SVD) could separate original signals into desired signals such as those from the substrate and cells. Additionally, an effect from a tilt of the substrate was investigated in this study. Separability of the proposed filter was evaluated by two investigations. First one was to evaluate the separability by estimating a correlation coefficient between the filtered signal and signal reflected from a position only with the substrate. Second one was to compare a slope of the substrate estimated from the original signal with that estimated from the filtered signals from the substrate. The experimental results showed that the proposed filter could separate signals from the substrate, and the compensation of the tilt of the substrate could improve the performance of the proposed filter.

Measurement and visualization of cell membrane surface charge in fixed cultured cells related with cell morphology

The diagnosis of patients with malignancies relies on the results of a clinical cytological examination. To enhance the diagnostic qualities of cytological examinations, it is important to have a detailed analysis of the cell’s characteristics. There is, therefore, a need for developing a new auxiliary method for cytological diagnosis. In this study, we focused on studying the charge of the cell membrane surface of fixed cells, which is one of important cell’s characteristics. Although fixed cells lose membrane potential which is observed in living cells owing to ion dynamics, we hypothesized that fixed cells still have a cell membrane surface charge due to cell membrane components and structure. We used 5 cell lines in this study (ARO, C32TG, RT4, TK, UM-UC-14). After fixation with CytoRich Red, we measured the cell membrane surface charge of fixed cells in solution using zeta potential measurements and fixed cells on glass slides, visualizing it using antibody-labeled beads and positively-charged beads. Furthermore, we measured the cell membrane surface charge of fixed cells under different conditions, such as different solution of fixative, ion concentration, pH, and pepsin treatments. The zeta potential measurements and visualization using the beads indicated that the cell membrane surface of fixed cells was negatively charged, and also that the charge varied among fixed cells. The charge state was affected by the different treatments. Moreover, the number of cell-bound beads was small in interphase, anaphase, and apoptotic cells. We concluded that the negative cell membrane surface charge was influenced by the three-dimensional structure of proteins as well as the different types of amino acids and lipids on the cell membrane. Thus, cell surface charge visualization can be applied as a new auxiliary method for clinical cytological diagnosis. This is the first systematic report of the cell membrane surface charge of fixed cells.

Effect of Transportation on Cultured Limbal Epithelial Sheets for Worldwide Treatment of Limbal Stem Cell Deficiency

Limbal stem cell deficiency can be treated with transplantation of cultured human limbal epithelial cells (LEC). It can be advantageous to produce LEC in centralized labs and thereafter ship them to eye clinics. The present study used transport simulations of LEC to determine if vigorous shaking during transport altered the viability, morphology and phenotype during a 4 day-long storage of LEC with a previously described serum-free storage method. Inserts with LEC cultured on amniotic membranes were sutured to caps inside air-tight containers with generous amounts of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)-buffered minimal essential medium (MEM). The containers were distributed among the following testing conditions: 6 hours with full containers, 36 hours with full containers, 36 hours with container three quarters full of medium, and 36 hours with container full of medium containing a shear-protecting agent (Pluronic-F68). Compared to stored, but non-transported controls, no statistically significant changes in viability and immunohistochemical staining were observed. The epithelial sheets remained intact. However, an air-liquid interface in the containers reduced the number of desmosomes and hemi-desmosomes compared to the controls. In conclusion, cultured LEC sheets appear to endure vigorous shaking for at least 36 hours if the container is full.

Phenotypic Reversion of Smooth Muscle Cells in Hybrid Vascular Prostheses

Our purpose was to evaluate whether or not and when phenotypic modulation of smooth muscle cells (SMCs) in hybrid vascular prostheses preincorporated with SMCs occurs upon implantation. Two types of hybrid vascular grafts incorporated with vascular cells derived from canine jugular veins were prepared: grafts containing a collagen gel layer covered with an endothelial monolayer at the luminal surface (Model I graft) and those containing an endothelial monolayer and SMC multilayer (Model II graft). They were bilaterally implanted into carotid arteries of the same dogs from which the cells had been harvested for 2 wk (n = 3) and 12 wk (n = 3). The time-dependent changes in populations of three SMC phenotypes (synthetic, intermediate, and contractile) in the neoarterial layers were quantified by morphometric evaluation using a transmission electron microscope in hybrid vascular grafts. Before implantation, all the SMCs were of the synthetic phenotype. In Model II grafts at 2 wk, synthetic and intermediate SMCs were dominant especially in the luminal layer. On the other hand, neoarterial layers at 12 wk were dominated by contractile SMCs, which were evenly distributed throughout the entire neoarterial tissues. A markedly delayed phenotypic reversion was noted for the Model I grafts at 12 wk. In the hybrid grafts, during about 3 mo of implantation, neoarterial SMCs transformed from the synthetic to the contractile phenotypes, which was promoted by SMC incorporation.

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

Cell mechanics is a novel label-free biomarker for indicating cell states and pathological changes. The advent of atomic force microscopy (AFM) provides a powerful tool for quantifying the mechanical properties of single living cells in aqueous conditions. The wide use of AFM in characterizing cell mechanics in the past two decades has yielded remarkable novel insights in understanding the development and progression of certain diseases, such as cancer, showing the huge potential of cell mechanics for practical applications in the field of biomedicine. In this paper, we reviewed the utilization of AFM to characterize cell mechanics. First, the principle and method of AFM single-cell mechanical analysis was presented, along with the mechanical responses of cells to representative external stimuli measured by AFM. Next, the unique changes of cell mechanics in two types of physiological processes (stem cell differentiation, cancer metastasis) revealed by AFM were summarized. After that, the molecular mechanisms guiding cell mechanics were analyzed. Finally the challenges and future directions were discussed.

Preparation of crude rough microsomes from tissue culture cells

There are various procedures for isolating microsomal fractions from tissue culture cells. The essential conditions for each step of one procedure are described here. Notes for special circumstances are included so that the procedure can be modified according to the experimental purpose.

Dynamic changes in microtubule organization during division of the primitive dinoflagellate Oxyrrhis marina

The marine dinoflagellate Oxyrrhis marina has three major microtubular systems: the flagellar apparatus made of one transverse and one longitudinal flagella and their appendages, cortical microtubules, and intranuclear microtubules. We investigated the dynamic changes of these microtubular systems during cell division by transmission and scanning electron microscopy, and confocal fluorescent laser microscopy. During prophase, basal bodies, both flagella and their appendages were duplicated. In the round nucleus situated in the cell centre, intranuclear microtubules appeared radiating toward the centre of the nucleus from densities located in some nuclear pores. During metaphase, both daughter flagellar apparatus separated and moved apart along the main cell axis. Microtubules of ventral cortex were also duplicated and moved with the flagellar apparatus. The nucleus flattened in the longitudinal direction and became discoid-shaped close to the equatorial plane. Many bundles of microtubules ran parallel to the short axis of the nucleus (cell long axis), between which chromosomes were arranged in the same direction. During ana-telophase, the nucleus elongated along the longitudinal axis and took a dumbbell shape. At this stage a contractile ring containing actin was clearly observed in the equatorial cortex. The cortical microtubule network seemed to be cut into two halves at the position of the actin bundle. Shortly after, the nucleus divided into two nuclei, then the cell body was constricted at its equator and divided into one anterior and one posterior halves which were soon rebuilt to produce two cells with two full sets of cortical microtubules. From our observations, several mechanisms for the duplication of the microtubule networks during mitosis in O. marina are discussed.

Switchgrass (Panicum virgatum L.) cell suspension cultures: Establishment, characterization, and application

Switchgrass (Panicum virgatum L.) is a warm-season perennial grass that has received considerable attention as a potential dedicated biofuel and bioproduct feedstock. Genetic improvement of switchgrass is needed for better cellulosic ethanol production, especially to improve cellulose-to-lignin ratios. Cell suspension cultures offer an in vitro system for mutant selection, mass propagation, gene transfer, and cell biology. Toward this end, switchgrass cell suspension cultures were initiated from embryogenic callus obtained from genotype Alamo 2. They have been established and characterized with different cell type morphologies: sandy, fine milky, and ultrafine cultures. Characterization includes histological analysis using scanning electron microscopy, and utility using protoplast isolation. A high protoplast isolation rate of up to 10(6) protoplasts/1.0g of cells was achieved for the fine milky culture, whereas only a few protoplasts were isolated for the sandy and ultrafine cultures. These results indicate that switchgrass cell suspension type sizably impacts the efficiency of protoplast isolation, suggesting its significance in other applications. The establishment of different switchgrass suspension culture cell types provides the opportunity to gain insights into the versatility of the system that would further augment switchgrass biology research.

Association of Rad51 polymorphism with DNA repair in BRCA1 mutation carriers and sporadic breast cancer risk

BACKGROUND

Inter-individual variation in DNA repair capacity is thought to modulate breast cancer risk. The phenotypic mutagen sensitivity assay (MSA) measures DNA strand breaks in lymphocytes; women with familial and sporadic breast cancers have a higher mean number of breaks per cell (MBPC) than women without breast cancer. Here, we explore the relationships between the MSA and the Rad51 gene, which encodes a DNA repair enzyme that interacts with BRCA1 and BRCA2, in BRCA1 mutation carriers and women with sporadic breast cancer.

METHODS

Peripheral blood lymphoblasts from women with known BRCA1 mutations underwent the MSA (n = 138 among 20 families). BRCA1 and Rad51 genotyping and sequencing were performed to identify SNPs and haplotypes associated with the MSA. Positive associations from the study in high-risk families were subsequently examined in a population-based case-control study of breast cancer (n = 1170 cases and 2115 controls).

RESULTS

Breast cancer diagnosis was significantly associated with the MSA among women from BRCA1 families (OR = 3.2 95%CI: 1.5-6.7; p = 0.004). The Rad51 5'UTR 135 C>G genotype (OR = 3.64; 95% CI: 1.38, 9.54; p = 0.02), one BRCA1 haplotype (p = 0.03) and in a polygenic model, the E1038G and Q356R BRCA1 SNPs were significantly associated with MBPC (p = 0.009 and 0.002, respectively). The Rad51 5'UTR 135C genotype was not associated with breast cancer risk in the population-based study.

CONCLUSIONS

Mutagen sensitivity might be a useful biomarker of penetrance among women with BRCA1 mutations because the MSA phenotype is partially explained by genetic variants in BRCA1 and Rad51.

Ultrastructure of Felis catus whole fetus (Fcwf-4) cell culture following infection with feline coronavirus

Feline coronavirus (FCoV) consists of two biotypes based on their growth in cell culture and their antigenicity. Infections with FCoV are highly prevalent in the cat population worldwide. In this study, Felis catus whole fetus (Fcwf-4)cell culture was infected with FCoV UPM11C/08. Virus multiplication in cell culture was monitored and examined under the transmission electron microscope. The virus particles revealed the characteristic morphology of feline FCoV represented by envelope viruses surrounded by peplomers. Virus attachment and entry into the cell occurred 15 h post-infection (pi), and the myriad of virus particles were observed both extracellularly and intracellularly after 48 h pi. Thereafter, intracellular virus particles were observed to be present in vacuoles or present freely in the cytoplasm.

[Hopping probe scanning ion conductance microscopy and its applications to topological imaging of live neuronal cells]

As a new kind of non-contacting high-resolution scanning probe microscopy, hopping probe scanning ion conductance microscopy (HPSICM) overcomes the disadvantages of the continuous feedback-control scanning mode of the conventional scanning ion conductance microscopy (SICM), which has been restricted to imaging relatively flat biological samples. The basic operation principles of HPSICM were briefly introduced in this paper. Then the high-resolution 3D morphological images of the two live neuronal cell lines, SK-N-SH cells and NGF-differentiated neurite PC12 cells, were respectively acquired in their physiological culture environment using HPSICM. It is demonstrated that HPSICM provides a powerful microscopy for in-depth studying the microstructures and their dynamic changes of live neuronal cells in real time.

Cytogenetic aberrations in primary cell cultures of the ovarian surface epithelium

Our objective was to determine the presence of chromosomal abnormalities in primary cultures of ovarian surface epithelial cells in women of different ages with no history of cancer. Throughout conventional cytogenetic techniques, we analyzed chromosome spreads of cultured ovarian epithelial cells from 10 donors who were 50 or more years old (B) and 16 controls between 20 and 49 years old (A), belonging to the mestizo population in Bogota DC, Colombia. Of the 26 cultures that were analyzed in passage 1, 61.5% had an abnormal chromosome complement (62.5% in A, and 60% in B). Abnormalities included polyploidies, endoduplications and monosomies. Deletions in chromosomes 3 and 11 were found in just one metaphase. None of the samples showed weaknesses or breakpoints. After transforming and applying the exact student's t-test for variance heterogeneity, we found significant differences in the frequency of metaphases, that were higher in A than in B (p=0.05), and in the frequency of polyploidies, which were higher in B than in A (p=0.044). Through the application of the Mann-Whitney test, we determined that the frequency of endoduplications was higher in A than in B (p=0.126), without reaching significant differences. There were no significant differences in the frequency of monosomies. The level of significance was set at p < or = 0.05. Taking into account that polyploidization is a marker of chromosomal instability and that the risk of cancer arising from the ovarian surface epithelium augments substantially after menopause, the increase in the frequency of age-associated polyploidies could be used as a predictor of ovarian cancer in women from an ethnically homogeneous population as the mestizo one in Bogota DC.

Assays for mitotic chromosome condensation in live yeast and mammalian cells

The dynamic reorganization of chromatin into rigid and compact mitotic chromosomes is of fundamental importance for faithful chromosome segregation. Owing to the difficulty of investigating this process under physiological conditions, the exact morphological transitions and the molecular machinery driving chromosome condensation remain poorly defined. Here, we review how imaging-based methods can be used to quantitate chromosome condensation in vivo, focusing on yeast and animal tissue culture cells as widely used model systems. We discuss approaches how to address structural dynamics of condensing chromosomes and chromosome segments, as well as to probe for mechanical properties of mitotic chromosomes. Application of such methods to systematic perturbation studies will provide a means to reveal the molecular networks underlying the regulation of mitotic chromosome condensation.

Condensin: Architect of mitotic chromosomes

Condensin is a highly conserved pentameric complex consisting of two structural maintenance of chromosome (SMC) ATPase subunits and three auxiliary components. While initially regarded as a key driver of mitotic chromosome condensation, condensin is increasingly viewed as having a more subtle influence on chromosome architecture. The two condensin complexes are required to direct the correct folding and organization of chromosomes prior to anaphase and for keeping the chromosomes compact as they separate to the poles. This ancient complex is essential in mitosis and meiosis and has additional roles in gene regulation and DNA repair. The wide variety of biochemical and genetic tools available are gradually unravelling the numerous roles condensin plays during the cell cycle and shedding light on its mechanism of action.

Cohesin, gene expression and development: lessons from Drosophila

The cohesin complex, discovered through its role in sister chromatid cohesion, also plays roles in gene expression and development in organisms from yeast to human. This review highlights what has been learned about the gene control and developmental functions of cohesin and the Nipped-B (NIPBL/Scc2) cohesin loading factor in Drosophila. The Drosophila studies have provided unique insights into the aetiology of Cornelia de Lange syndrome (CdLS), which is caused by mutations affecting sister chromatid cohesion proteins in humans. In vivo experiments with Drosophila show that cohesin and Nipped-B have dosage-sensitive effects on the functions of many evolutionarily conserved genes and developmental pathways. Genome-wide studies with Drosophila cultured cells show that Nipped-B and cohesin co-localize on chromosomes, and bind preferentially, but not exclusively, to many actively transcribed genes and their regulatory sequences, including many of the proposed in vivo target genes. In contrast, the cohesion factors are largely excluded from genes silenced by Polycomb group (PcG) proteins. Combined, the in vivo genetic data and the binding patterns of cohesin and Nipped-B in cultured cells are consistent with the hypothesis that they control the action of gene regulatory sequences, including transcriptional enhancers and insulators, and suggest that they might also help define active chromatin domains and influence transcriptional elongation.

Iron starvation and culture age activate metacaspases and programmed cell death in the marine diatom Thalassiosira pseudonana

In the modern ocean, phytoplankton maintain extremely high primary production/biomass ratios, indicating that they bloom, die, and are replaced weekly. The molecular mechanisms regulating cellular mortality and turnover are largely unknown, even though they effectively short-circuit carbon export to the deep ocean and channel primary productivity to microbial food webs. Here, we present morphological, biochemical, and molecular evidence of caspase-mediated, autocatalytic programmed cell death (PCD) in the diatom Thalassiosira pseudonana in response to iron starvation. Transmission electron microscopy revealed internal degradation of nuclear, chloroplastic, and mitochondrial organelles, all while the plasma membranes remained intact. Cellular degradation was concomitant with dramatic decreases in photosynthetic efficiency, externalization of phosphatidylserine, and significantly elevated caspase-specific activity, with the addition of a broad-spectrum caspase inhibitor rescuing cells from death. A search of the T. pseudonana genome identified six distinct putative metacaspases containing a conserved caspase domain structure. Quantitative reverse transcription-PCR and Western blot analysis revealed differential gene and protein expression of T. pseudonana metacaspases, some of which correlated with physiological stress and caspase activity. Taken together with the recent discovery of the metacaspase-mediated viral infection of phytoplankton (K. D. Bidle, L. Haramaty, J. Barcelos-Ramos, and P. G. Falkowski, Proc. Natl. Acad. Sci. USA 104:6049-6054, 2007), our findings reveal a key role for metacaspases in the turnover of phytoplankton biomass in the oceans. Furthermore, given that Fe is required for photosynthetic electron transfer and is chronically limiting in a variety of oceanic systems, including high-nutrient low-chlorophyll regions, our findings provide a potential ecological context for PCD in these unicellular photoautotrophs.

BNIP3 is an RB/E2F target gene required for hypoxia-induced autophagy

Hypoxia and nutrient deprivation are environmental stresses governing the survival and adaptation of tumor cells in vivo. We have identified a novel role for the Rb tumor suppressor in protecting against nonapoptotic cell death in the developing mouse fetal liver, in primary mouse embryonic fibroblasts, and in tumor cell lines. Loss of pRb resulted in derepression of BNip3, a hypoxia-inducible member of the Bcl-2 superfamily of cell death regulators. We identified BNIP3 as a direct target of pRB/E2F-mediated transcriptional repression and showed that pRB attenuates the induction of BNIP3 by hypoxia-inducible factor to prevent autophagic cell death. BNIP3 was essential for hypoxia-induced autophagy, and its ability to promote autophagosome formation was enhanced under conditions of nutrient deprivation. Knockdown of BNIP3 reduced cell death, and remaining deaths were necrotic in nature. These studies identify BNIP3 as a key regulator of hypoxia-induced autophagy and suggest a novel role for the RB tumor suppressor in preventing nonapoptotic cell death by limiting the extent of BNIP3 induction in cells.

Selenium deficiency alters epithelial cell morphology and responses to influenza

It is unknown whether nutritional deficiencies affect the morphology and function of structural cells, such as epithelial cells, and modify the susceptibility to viral infections. We developed an in vitro system of differentiated human bronchial epithelial cells (BEC) grown either under selenium-adequate (Se+) or selenium-deficient (Se-) conditions, to determine whether selenium deficiency impairs host defense responses at the level of the epithelium. Se- BECs had normal SOD activity, but decreased activity of the selenium-dependent enzyme GPX1. Interestingly, catalase activity was also decreased in Se- BECs. Both Se- and Se+ BECs differentiated into a mucociliary epithelium; however, Se- BEC demonstrated increased mucus production and increased Muc5AC mRNA levels. This effect was also seen in Se+ BEC treated with 3-aminotriazole, an inhibitor of catalase activity, suggesting an association between catalase activity and mucus production. Both Se- and Se+ were infected with influenza A/Bangkok/1/79 and examined 24 h postinfection. Influenza-induced IL-6 production was greater while influenza-induced IP-10 production was lower in Se- BECs. In addition, influenza-induced apoptosis was greater in Se- BEC as compared to the Se+ BECs. These data demonstrate that selenium deficiency has a significant impact on the morphology and influenza-induced host defense responses in human airway epithelial cells.

Chromatid-type aberrations following irradiation in G0 lymphocytes with heavy ions

We describe a low level of chromatid-type aberrations which included the relatively rare isochromatid/chromatid triradial in peripheral blood lymphocytes that were irradiated, ostensibly in G0, with accelerated heavy (12)C ions. These were produced only at the energies of 69 MeV/n (34.6 keV/microm), almost absent at the energy of either 58.6 MeV/n (46.07 keV/ microm) or 19.3 MeV/n (97 keV/microm), nor were they found after low-LET X-rays. Mechanisms potentially responsible for their formation are discussed.

Establishment and biochemical characterization of primary cells of the upper aerodigestive tract

The upper aerodigestive tract, composed of the oral cavity, the pharynx and the esophagus, is a complex system whose components function in both organ-specific ways as well in serving as a protective barrier against the enzymes which initiate digestion as well as against the mechanical functions which serve to ensure movement of food through the upper aerodigestive tract. Given these diverse functional requirements, the study of the anatomy and physiology of this region are uniquely complex and significantly understudied. The goal of the current study was to develop a simple and reproducible method for the isolation, growth, and maintenance of primary epithelial cells from the oral cavity, the pharynx and the esophagus. In addition, given the increased interest in diseases characterized by a loss of mucosal integrity in these areas which is often accompanied by a diminished wound healing capability, these cells were biochemically characterized with a focus on the components of the extracellular matrix remodeling axis including the activity and inhibition of the matrix metalloproteinases (MMPs).

Zoo-FISH in the European mole (Talpa europaea) detects all ancestral Boreo-Eutherian human homologous chromosome associations

Zoo-FISH with human whole-chromosome paint probes delineated syntenic association of human homologous chromosome segments 3-21, 14-15, 16-19, 4-8, 7-16 and 12-22 (twice) in the European mole (Talpa europaea, Talpidae, Eulipotyphla, Mammalia). These segment associations represent shared ancestral Boreo-Eutherian traits, half of which were previously not described for Eulipotyphla. The karyotype of the European mole acquired a minimum of 19 translocations and six inversions compared to the presumed Boreo-Eutherian ancestor.

Karyotype relationships of six bat species (Chiroptera, Vespertilionidae) from China revealed by chromosome painting and G-banding comparison

The Vespertilionidae is the largest family in the order Chiroptera and has a worldwide distribution in the temperate and tropical regions. In order to further clarify the karyotype relationships at the lower taxonomic level in Vespertilionidae, genome-wide comparative maps have been constructed between Myotis myotis (MMY, 2n = 44) and six vesper bats from China: Myotis altarium (MAL, 2n = 44), Hypsugo pulveratus (HPU, 2n = 44), Nyctalus velutinus (NVE, 2n = 36), Tylonycteris robustula (TRO, 2n = 32), Tylonycteris sp. (TSP, 2n = 30)and Miniopterus fuliginosus (MFU, 2n = 46) by cross-species chromosome painting with a set of painting probes derived from flow-sorted chromosomes of Myotis myotis. Each Myotis myotis autosomal probe detected a single homologous chromosomal segment in the genomes of these six vesper bats except for MMY chromosome 3/4 paint which hybridized onto two chromosomes in the genome of M. fuliginosus. Our results show that Robertsonian translocation is the main mode of karyotype evolution in Vespertilionidae and that the addition of heterochromatic material also plays an important role in the karyotypic evolution of the genera Tylonycteris and Nyctalus. Two conserved syntenic associations (MMY9 + 23 and 18 + 19) could be the synapomorphic features for the genus Tylonycteris. The integration of our maps with the published maps has enabled us to deduce chromosomal homologies between human and these six vesper bats and provided new insight into the karyotype evolution of the family Vespertilionidae.

Assignment of linkage groups to turkey chromosome 1 (MGA1)

Previous genetic mapping identified three linkage groups (M1, M18 and M26) in the turkey corresponding to chicken chromosome 1 (GGA1). This is inconsistent with previously described chromosomal differences between these species. FISH analysis of BAC clones corresponding to microsatellite markers from each of the three turkey linkage groups, assigned all three linkage groups to a single chromosome (MGA1).

Bioreactor for mammalian cell culture

Purpose of this article is to review the current status of bioreactor design for mammalian cell culture. Morphological and biochemical features of two major mammalian cell groups, anchorage-dependent and independent cells are proposed as a basis for different behavior at their cultivation. Different bioreactor configurations are systematically discussed through enumerating elementary physical phenomena and through stressing their physiological significance. Special considerations are given to those areas which are inherent to mammalian cell bioreactor.

Effects of Cellular Fine Structure on Scattered Light Pattern

Biological cells are complex in both morphological and biochemical structure. The effects of cellular fine structure on light scattered from cells are studied by employing a three-dimensional code named AETHER which solves the full set of Maxwell equations by using the finite-difference time-domain method. It is shown that changes in cellular fine structure can cause significant changes in the scattered light pattern over particular scattering angles. These changes potentially provide the possibility for distinguishability of cellular intrastructures. The effects that features of different intrastructure have on scattered light are discussed from the viewpoint of diagnosing cellular fine structure. Finally, we discuss scattered light patterns for lymphocyte-like cells and basophil-like cells.

Thrombopoietin protects against in vitro and in vivo cardiotoxicity induced by doxorubicin

BACKGROUND

Doxorubicin (DOX) is an important antineoplastic agent. However, the associated cardiotoxicity, possibly mediated by the production of reactive oxygen species, has remained a significant and dose-limiting clinical problem. Our hypothesis is that the hematopoietic/megakaryocytopoietic growth factor thrombopoietin (TPO) protects against DOX-induced cardiotoxicity and might involve antiapoptotic mechanism exerted on cardiomyocytes.

METHODS AND RESULTS

In vitro investigations on H9C2 cell line and spontaneously beating cells of primary, neonatal rat ventricle, as well as an in vivo study in a mouse model of DOX-induced acute cardiomyopathy, were performed. Our results showed that pretreatment with TPO significantly increased viability of DOX-injured H9C2 cells and beating rates of neonatal myocytes, with effects similar to those of dexrazoxane, a clinically approved cardiac protective agent. TPO ameliorated DOX-induced apoptosis of H9C2 cells as demonstrated by assays of annexin V, active caspase-3, and mitochondrial membrane potential. In the mouse model, administration of TPO (12.5 microg/kg IP for 3 alternate days) significantly reduced DOX-induced (20 mg/kg) cardiotoxicity, including low blood cell count, cardiomyocyte lesions (apoptosis, vacuolization, and myofibrillar loss), and animal mortality. Using Doppler echocardiography, we observed increased heart rate, fractional shortening, and cardiac output in animals pretreated with TPO compared with those receiving DOX alone.

CONCLUSIONS

These data have provided the first evidence that TPO is a protective agent against DOX-induced cardiac injury. We propose to further explore an integrated program, incorporating TPO with other protocols, for treatment of DOX-induced cardiotoxicity and other forms of cardiomyopathy.

Regulation of dendritic branching and spine maturation by semaphorin3A-Fyn signaling

A member of semaphorin family, semaphorin3A (Sema3A), acts as a chemorepellent or chemoattractant on a wide variety of axons and dendrites in the development of the nervous systems. We here show that Sema3A induces clustering of both postsynaptic density-95 (PSD-95) and presynaptic synapsin I in cultured cortical neurons without changing the density of spines or filopodia. Neuropilin-1 (NRP-1), a receptor for Sema3A, is present on both axons and dendrites. When the cultured neurons are exposed to Sema3A, the cluster size of PSD-95 is markedly enhanced, and an extensive colocalization of PSD-95 and NRP-1 or actin-rich protrusion is seen. The effects of Sema3A on spine morphology are blocked by PP2, an Src type tyrosine kinase inhibitor, but not by the PP3, the inactive-related compound. In the cultured cortical neurons from fyn(-/-) mice, dendrites bear few spines, and Sema3A does not induce PSD-95 cluster formation on the dendrites. Sema3A and its receptor genes are highly expressed during the synaptogenic period of postnatal days 10 and 15. The cortical neurons in layer V, but not layer III, show a lowered density of synaptic bouton-like structure on dendrites in sema3A- and fyn-deficient mice. The neurons of the double-heterozygous mice show the lowered spine density, whereas those of single heterozygous mice show similar levels of the spine density as the wild type. These findings suggest that the Sema3A signaling pathway plays an important role in the regulation of dendritic spine maturation in the cerebral cortex neurons.

Site-specific 3D imaging of cells and tissues with a dual beam microscope

Current approaches to 3D imaging at subcellular resolution using confocal microscopy and electron tomography, while powerful, are limited to relatively thin and transparent specimens. Here we report on the use of a new generation of dual beam electron microscopes capable of site-specific imaging of the interior of cellular and tissue specimens at spatial resolutions about an order of magnitude better than those currently achieved with optical microscopy. The principle of imaging is based on using a focused ion beam to create a cut at a designated site in the specimen, followed by viewing the newly generated surface with a scanning electron beam. Iteration of these two steps several times thus results in the generation of a series of surface maps of the specimen at regularly spaced intervals, which can be converted into a three-dimensional map of the specimen. We have explored the potential of this sequential "slice-and-view" strategy for site-specific 3D imaging of frozen yeast cells and tumor tissue, and establish that this approach can identify the locations of intracellular features such as the 100 nm-wide yeast nuclear pore complex. We also show that 200 nm thick sections can be generated in situ by "milling" of resin-embedded specimens using the ion beam, providing a valuable alternative to manual sectioning of cells and tissues using an ultramicrotome. Our results demonstrate that dual beam imaging is a powerful new tool for cellular and subcellular imaging in 3D for both basic biomedical and clinical applications.

Thalidomide attenuates nitric oxide mediated angiogenesis by blocking migration of endothelial cells

BACKGROUND

Thalidomide is an immunomodulatory agent, which arrests angiogenesis. The mechanism of anti-angiogenic activity of thalidomide is not fully understood. As nitric oxide is involved in angiogenesis, we speculate a cross-talk between thalidomide and nitric oxide signaling pathway to define angiogenesis. The aim of present study is to understand the mechanistic aspects of thalidomide-mediated attenuation of angiogenesis induced by nitric oxide at the cellular level.

METHODS

To study the cellular mechanism of thalidomide-mediated blocking of angiogenesis triggered by nitric oxide, we used two endothelial cell based models: 1) wound healing and 2) tube formation using ECV 304, an endothelial cell line. These cell-based models reflect pro-angiogenic events in vivo. We also studied the effects of thalidomide on nitric oxide mediated egg yolk angiogenesis. Thalidomide could block the formation of blood vessels both in absence and presence of nitric oxide. Thalidomide effects on migration of, and actin polymerization in, ECV 304 cells were studied at the single cell level using live cell imaging techniques and probes to detect nitric oxide.

RESULTS

Results demonstrate that thalidomide blocks nitric oxide-mediated angiogenesis in egg yolk model and also reduces the number of tubes formed in endothelial cell monolayers. We also observed that thalidomide arrests wound healing in presence and absence of nitric oxide in a dose-dependent fashion. Additionally, thalidomide promotes actin polymerization and antagonizes the formation of membrane extensions triggered by nitric oxide in endothelial cells. Experiments targeting single tube structure with thalidomide, followed by nitric oxide treatment, show that the tube structures are insensitive to thalidomide and nitric oxide. These observations suggest that thalidomide interferes with nitric oxide-induced migration of endothelial cells at the initial phase of angiogenesis before cells co-ordinate themselves to form organized tubes in endothelial cells and thereby inhibits angiogenesis.

CONCLUSION

Thalidomide exerts inhibitory effects on nitric oxide-mediated angiogenesis by altering sub-cellular actin polymerization pattern, which leads to inhibition of endothelial cell migration.

Dendrites contain a spacing pattern

The distinctive branching patterns of dendritic arbors are essential for neuronal information processing. The final shape of an arbor is the result of intrinsic and extrinsic factors. However, the cellular mechanisms that underlie branch patterning are unknown. In many biological systems, locally acting factors are intrinsically organized into spacing patterns that guide patterned morphogenesis. Here, we show that neurons contain two types of periodic and regular elements (PADREN1s and PADREN2s) that are arranged into a spacing pattern. The wavelength of the pattern is approximately 20 microm. Dendritic branches occur preferentially within PADREN1s, and specific PADREN lengths correspond to specific arbor types. The lengths of the PADRENs also change over time and can be modified by activity. However, PADRENs are intrinsically organized, possibly by a reaction-diffusion process. PADRENs reveal a previously unrecognized level of neuronal organization that may provide insight into how the distinct branching patterns of the dendrites are intrinsically organized.

Imaging specific cell-surface proteolytic activity in single living cells

We describe a simple, sensitive and noninvasive assay that uses nontoxic, reengineered anthrax toxin-beta-lactamase fusion proteins with altered protease cleavage specificity to visualize specific cell-surface proteolytic activity in single living cells. The assay could be used to specifically image endogenous cell-surface furin, urokinase plasminogen activator and metalloprotease activity. We have adapted the assay for fluorescence microscopy, flow cytometry and fluorescent plate reader formats, and it is amenable for automation and high-throughput analysis.

Constitutively active cytoplasmic c-Jun N-terminal kinase 1 is a dominant regulator of dendritic architecture: role of microtubule-associated protein 2 as an effector

Normal functioning of the nervous system requires precise regulation of dendritic shape and synaptic connectivity. Here, we report a severe impairment of dendritic structures in the cerebellum and motor cortex of c-Jun N-terminal kinase 1 (JNK1)-deficient mice. Using an unbiased screen for candidate mediators, we identify the dendrite-specific high-molecular-weight microtubule-associated protein 2 (MAP2) as a JNK substrate in the brain. We subsequently show that MAP2 is phosphorylated by JNK in intact cells and that MAP2 proline-rich domain phosphorylation is decreased in JNK1-/- brain. We developed compartment-targeted JNK inhibitors to define whether a functional relationship exists between the physiologically active, cytosolic pool of JNK and dendritic architecture. Using these, we demonstrate that cytosolic, but not nuclear, JNK determines dendritic length and arbor complexity in cultured neurons. Moreover, we confirm that MAP2-dependent process elongation is enhanced after activation of JNK. Using JNK1-/- neurons, we reveal a dominant role for JNK1 over ERK in regulating dendritic arborization, whereas ERK only regulates dendrite shape under conditions in which JNK activity is low (JNK1-/- neurons). These results reveal a novel antagonism between JNK and ERK, potentially providing a mechanism for fine-tuning the dendritic arbor. Together, these data suggest that JNK phosphorylation of MAP2 plays an important role in defining dendritic architecture in the brain.

Netrin-1 induces axon branching in developing cortical neurons by frequency-dependent calcium signaling pathways

A single axon can innervate multiple targets by collateral branching. Axon branching is thus essential for establishing CNS connectivity. However, surprisingly little is known about the mechanisms by which branching is regulated. Axons often stop elongating before branches develop and anatomical and molecular data suggest that axon branching occurs independent of axon outgrowth. We found that netrin-1 dramatically increases cortical axon branching. Here, we sought to identify intracellular signaling components involved in netrin-1-induced axon branching. Using live cell imaging of dissociated developing cortical neurons, we show that netrin-1 rapidly increases the frequency of repetitive calcium transients. These transients are often restricted to small regions of the axon. Simultaneous imaging of calcium activity and development of axon branches revealed that Ca2+ transients coincide spatially and temporally with protrusion of branches from the axon. Remarkably, fully formed branches with motile growth cones could develop de novo within 20 min. Netrin-1-induced Ca2+ transients involve release from intracellular stores and Ca2+ signaling is essential for netrin-1-induced axon branching. Using techniques to overexpress or suppress kinase activity, we find that calcium/calmodulin-dependent protein kinase II (CaMKII) and mitogen-activated protein kinase (MAPK) are major downstream targets of the netrin-1 calcium signaling pathway and are required for axon branching. CaMKII, but not MAPK, is also involved in axon outgrowth. The role of CaMKII and MAPKs in axon branching is consistent with the sensitivity of these kinases to changes in the frequency Ca2+ transients. Together, these novel findings define calcium signaling mechanisms required for development of new axon branches promoted by a guidance cue.

Defining the transcriptome of accelerated and replicatively senescent keratinocytes reveals links to differentiation, interferon signaling, and Notch related pathways

Epidermal keratinocytes (KCs) undergo highly orchestrated morphological and molecular changes during transition from proliferative compartment into growth arrested early and late differentiation layers, prior to dying in outermost cornified layers of normal skin. Creation of stratum corneum is vital to barrier function protecting against infection. Transcriptional events in KCs regulating complex processes of differentiation and host defense required to maintain constant epidermal thickness and resistance to infection in either young or aged skin are largely unknown. Furthermore, as terminal differentiation is characterized by irreversible loss of replicative potential culminating in dead layers at the skin surface, this process may be viewed as a form of senescence. However, a complete transcriptional profile of senescent (SN) human KCs has not been previously defined to permit delineation of molecular boundaries involving differentiation and senescence. To fill this void, we utilized global transcriptional analysis of KCs maintained in vitro as either cultures of proliferating (PR) cells, early and late confluent (LC) (accelerated senescence) cultures, or KCs undergoing replicative senescence. Global gene expression profiling revealed early confluent (EC) KCs were somewhat similar to PR KCs, while prominent differences were evident when compared to LC KCs; which were also distinct from replicatively SN KCs. While confluent KCs have in common several genes regulating differentiation with replicatively SN KCs, the latter cells expressed elevated levels of genes involved in interferon signaling and inflammatory pathways. These results provide new insights into cell autonomous transcriptional-based programs operative within KCs contributing to replicative senescence, with partial sharing of genes involved in differentiation. In addition, regulation of KC senescence may involve participation of interferon signaling pathways derived from the important role of KCs in protecting skin from infection. Integrating all of the transcriptional data revealed a key role for Notch receptor mediated signaling in the confluency induced differentiation phenotype using this model system.

A comparison of Shiga-toxin negative Escherichia coli O157 aflagellate and intimin deficient mutants in porcine in vitro and in vivo models of infection

Isolation of Shiga-toxin (Stx) positive Escherichia coli O157:H7 from commercially grown pigs has been reported. Furthermore, experimental infection studies have demonstrated that Stx-positive E. coli O157:H7 can persist in 12-week-old experimentally orally inoculated conventional pigs for up to 2 months and that persistence was not dependent upon intimin. We have shown that the flagellum of Stx-negative E. coli O157:H7 does not have a role to play in pathogenesis in ruminant models whereas, in poultry, the flagellum of E. coli O157:H7 was important for long-term persistent infection. The contribution of the flagellum of Stx-negative E. coli O157 in the colonisation of pigs was investigated by adherence assays on a porcine (IPI-21) cell line, porcine in vitro organ culture (IVOC) and experimental oral inoculation of conventional 14-week-old pigs. E. coli O157:H7 NCTC12900nal(r) and isogenic aflagellate and intimin deficient mutants adhered equally well to IPI-21 cells. In porcine IVOC association assays, E. coli O157:H7 NCTC12900nal(r) was associated in significantly higher numbers to tissues from the caecum and the terminal rectum than other sites. The aflagellate and intimin deficient mutants significantly adhered in greater numbers to more IVOC gastrointestinal tissues than the parent. Groups of 14-week-old pigs were dosed orally with 10(10)CFU/10ml of either E. coli O157:H7 NCTC12900nal(r) or isogenic aflagellate and intimin deficient mutants and recovery of each test strain was similar. Histological analysis of pig tissues at post mortem examination revealed that E. coli O157 specifically stained bacteria were associated with the mucosa of the ascending and spiral colon. These data suggest that colonisation and persistence of Stx-negative E. coli O157:H7 in pigs, involves mechanisms that do not require the flagellum or intimin.

Conditioning injury-induced spinal axon regeneration requires signal transducer and activator of transcription 3 activation

Sensory axons in the adult spinal cord do not regenerate after injury. This is essentially because of inhibitory components in the damaged CNS, such as myelin-associated inhibitors and the glial scar. However, if the sciatic nerve is axotomized before injury of the dorsal column, injured axons can regenerate a short distance in the spinal cord. Here, we show that sciatic nerve transection results in time-dependent phosphorylation and activation of the transcription factor, signal transducer and activator of transcription 3 (STAT3), in dorsal root ganglion (DRG) neurons. This effect is specific to peripheral injuries and does not occur when the dorsal column is crushed. Sustained perineural infusion of the Janus kinase 2 (JAK2) inhibitor AG490 to the proximal nerve stump can block STAT3 phosphorylation after sciatic nerve transection and results in reduced growth-associated protein 43 upregulation and compromised neurite outgrowth in vitro. Importantly, in vivo perineural infusion of AG490 also significantly attenuates dorsal column axonal regeneration in the adult spinal cord after a preconditioning sciatic nerve transection. We conclude that STAT3 activation is necessary for increased growth ability of DRG neurons and improved axonal regeneration in the spinal cord after a conditioning injury.

Phospholipase D1-promoted release of tissue plasminogen activator facilitates neurite outgrowth

Temporal lobe epilepsy (TLE) is the most common form of epilepsy, affecting approximately 1-2% of the population. Seizure events resulting from TLE are characterized by aberrant hippocampal mossy fiber sprouting and plastic responses that affect brain function. Seizure susceptibility is modulated by the enzyme tissue plasminogen activator (tPA), the normal physiological role of which includes promotion of synaptic reorganization in the mossy fiber pathway by initiating a proteolytic cascade that cleaves extracellular matrix components and influences neurite extension. tPA is concentrated at and selectively secreted from growth cones during excitatory events. However, the mechanisms underlying tPA release during seizure-induced synaptogenesis are not well understood. We examine here potential roles for the signaling enzyme phospholipase D1 (PLD1), which promotes regulated exocytosis in non-CNS cell types, and which we previously demonstrated increases in expression in hippocampal neurons during seizure-induced mossy fiber sprouting. We now show that overexpression of wild-type PLD1 in cultured neurons promotes tPA release and tPA-dependent neurite extension, whereas overexpression of an inactive PLD1 allele or pharmacological inhibition of PLD1 inhibits tPA release. Similarly, viral delivery of wild-type PLD1 into the hippocampus facilitates tPA secretion and mossy fiber sprouting in a seizure-inducing model, whereas the inactive PLD1 allele inhibits tPA release and elicits blunted and abnormal mossy fiber extension similar to that observed for tPA-/- mice. Together, these findings secretion and thus mossy fiber extension in the setting of elevated suggest that PLD1 functions endogenously to regulate tPA-/- neuronal stimulation, such as that seen in TLE.

Edg8/S1P5: an oligodendroglial receptor with dual function on process retraction and cell survival

Endothelial differentiation gene (Edg) proteins are G-protein-coupled receptors activated by lysophospholipid mediators: sphingosine-1-phosphate (S1P) or lysophosphatidic acid. We show that in the CNS, expression of Edg8/S1P5, a high-affinity S1P receptor, is restricted to oligodendrocytes and expressed throughout development from the immature stages to the mature myelin-forming cell. S1P activation of Edg8/S1P5 on O4-positive pre-oligodendrocytes induced process retraction via a Rho kinase/collapsin response-mediated protein signaling pathway, whereas no retraction was elicited by S1P on these cells derived from Edg8/S1P5-deficient mice. Edg8/S1P5-mediated process retraction was restricted to immature cells and was no longer observed at later developmental stages. In contrast, S1P activation promoted the survival of mature oligodendrocytes but not of pre-oligodendrocytes. The S1P-induced survival of mature oligodendrocytes was mediated through a pertussis toxin-sensitive, Akt-dependent pathway. Our data demonstrate that Edg8/S1P5 activation on oligodendroglial cells modulates two distinct functional pathways mediating either process retraction or cell survival and that these effects depend on the developmental stage of the cell.

A truncated tropomyosin-related kinase B receptor, T1, regulates glial cell morphology via Rho GDP dissociation inhibitor 1

Through tropomyosin-related kinase B (TrkB) receptors, brain-derived neurotrophic factor (BDNF) performs many biological functions such as neural survival, differentiation, and plasticity. T1, an isoform of TrkB receptors that lacks a tyrosine kinase, predominates in the adult mammalian CNS, yet its role remains controversial. In this study, to examine whether T1 transduces a signal and to determine its function, we first performed an affinity purification of T1-binding protein with the T1-specific C-terminal peptide and identified Rho GDP dissociation inhibitor 1 (GDI1), a GDP dissociation inhibitor of Rho small G-proteins, as a signaling protein directly associated with T1. The binding of BDNF to T1 caused Rho GDI1 to dissociate from the C-terminal tail of T1. Astrocytes cultured for 30 d expressed only endogenous T1 among the BDNF receptors. In 30 d cultured astrocytes, Rho GDI1, when dissociated in a BDNF-dependent manner, controlled the activities of the Rho GTPases, which resulted in rapid changes in astrocytic morphology. Furthermore, using 2 d cultured astrocytes that were transfected with T1, a T1 deletion mutant, or cyan fluorescent protein fusion protein of the T1-specific C-terminal sequence, we demonstrated that T1-Rho GDI1 signaling was indispensable for regulating the activities of Rho GTPases and for the subsequent morphological changes among astrocytes. Therefore, these findings indicate that the T1 signaling cascade can alter astrocytic morphology via regulation of Rho GTPase activity.

Fidelity of micropatterned cell cultures

Methods that enable the culture of micropatterned cells may help advance our fundamental understanding of cell-cell and cell-surface interactions, while facilitating the development and implementation of cell-based biological assays. However, the long-term stability of the cell patterns can limit the time scales over which such methods can be informative. Here we used self-assembling monolayers (SAMs) to localize the adsorption of baby hamster kidney (BHK-21) cells as well as cells from a murine astrocytoma-derived cell line (delayed brain tumor) in linear arrays. We tested the effects of surface chemistries, fibronectin pre-treatments, array dimensions, and cell types on pattern fidelity. Changes in patterns were monitored by phase-contrast microscopy up to 96 h post-plating, followed by digital imaging, and these changes were quantified by measuring an "intrusion distance" or the average distance cells extend beyond the initial adhesive/non-adhesive boundary. Loss of pattern boundaries involved different mechanisms for different cells. Treatment of patterned surfaces with fibronectin prior to plating of cells tended to promote earlier loss of pattern fidelity, and the extent of pattern loss was further augmented for SAMs formed using hydrophobic monolayers. Finally, reduction of gap spacing between adjacent cell arrays promoted pattern loss.

Karyotype and molecular cytogenetic studies in polycythemia vera

A minority of patients with newly diagnosed polycythemia vera (PV) have an abnormal karyotype in their myeloid cells but no invariant chromosomal aberration has been found. The most frequent visible alteration is a 20q deletion, also characterized in other myeloproliferative diseases (MPD) and myeloid malignancies; among other chromosomal changes, trisomy 9 appears more common in PV than in other MPDs. When a myelofibrosis complicates the course of the disease, cytogenetic anomalies become quite common with a striking frequency of partial duplication 1q; an evolution towards myelodysplasia or acute leukemia is almost always associated with nonspecific chromosomal aberrations. Modern cytogenetic methods have disclosed cryptic anomalies and pointed out the high frequency of 9p alterations affecting a restricted region, thus stimulating an active search for candidate genes or specific mutations.

Chronic ethanol induces synaptic but not extrasynaptic targeting of NMDA receptors

The development of ethanol tolerance and dependence reflects neuroadaptive changes in response to continuous depression in synaptic activity. The present study used confocal imaging and electrophysiology procedures to assess the effects of prolonged ethanol exposure on NMDA receptor trafficking in cultures of hippocampal neurons. Neurons exposed to 50 mm ethanol for 4 d showed an increase in the colocalization of NMDA receptor type 1 (NR1) clusters with the presynaptic marker protein synapsin. This was accompanied by significant increases in the size and density of these synapsin-associated clusters with no change observed in nonsynapsin-associated NR1 clusters. Similar effects were observed with NR2B clustering after chronic ethanol exposure. The increase in synaptic NMDA receptor clustering was prevented by addition of a protein kinase A inhibitor or by coexposure to a low concentration of NMDA and was reversed when ethanol was removed from the cultures. No changes were observed in the synaptic content, cluster size, or density of AMPA receptors after ethanol exposure. Electrophysiological measurements on ethanol-treated neurons revealed a similar enhancement in synaptic NMDA currents with no change in AMPA-mediated events. After isolation of extrasynaptic NMDA receptors by MK801 (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate (/) trapping, whole-cell responses to NMDA were not different between control and ethanol-treated neurons These observations demonstrate that neuroadaptive changes in NMDA receptors in response to prolonged ethanol exposure occur through activity-dependent processes that regulate their synaptic targeting and localization.

Cytokeratin changes in cell culture systems of epithelial cells isolated from oral mucosa: a short review

In the past three decades, many studies have analyzed ultrastructural and molecular markers of differentiation in squamous stratified epithelial tissues. In these tissues, epithelial cells migrating from the basal layer to the upper layers undergo drastic changes, which involve membrane-associated proteins, DNA synthesis, phenotypic aspects, lipid composition, and cytoskeletal components. Cytoskeletal components include a large and heterogeneous group, including intermediate filaments, components of the cornified envelope, and of the stratum corneum. When grown in mono- and multilayer cell cultures, epithelial cells isolated from the oral mucosa may reproduce many of the biochemical and morphological aspects of epithelial tissue in vivo. In the present paper, we examine phenotypic changes, development of suprabasal layer, and Involucrin expression occurring in differentiating oral epithelial cells, based on literature review and original data.